Generally, when completing a subterranean well for the production of fluids, minerals, or gases from underground reservoirs, several types of tubulars are placed downhole as part of the drilling, exploration, and completions process. These tubulars can include casing, tubing, pipes, liners, and devices conveyed downhole by tubulars of various types. Each well is unique, so combinations of different tubulars may be lowered into a well for a multitude of purposes.
A subsurface or subterranean well transits one or more formations. The formation is a body of rock or strata that contains one or more compositions. The formation is treated as a continuous body. Within the formation hydrocarbon deposits may exist. Typically a wellbore will be drilled from a surface location, placing a hole into a formation of interest. Completion equipment will be put into place, including casing, tubing, and other downhole equipment as needed. Perforating the casing and the formation with a perforating gun is a well known method in the art for accessing hydrocarbon deposits within a formation from a wellbore.
Explosively perforating the formation using a shaped charge is a widely known method for completing an oil well. A shaped charge is a term of art for a device that when detonated generates a focused explosive output. This is achieved in part by the geometry of the explosive in conjunction with an adjacent liner. Generally, a shaped charge includes a metal case that contains an explosive material with a concave shape, which has a thin metal liner on the inner surface. Many materials are used for the liner; some of the more common metals include brass, copper, tungsten, and lead. When the explosive detonates the liner metal is compressed into a super-heated, super pressurized jet that can penetrate metal, concrete, and rock. Perforating charges are typically used in groups. These groups of perforating charges are typically held together in an assembly called a perforating gun. Perforating guns come in many styles, such as strip guns, capsule guns, port plug guns, and expendable hollow carrier guns.
Perforating charges are typically detonated by detonating cord in proximity to a priming hole at the apex of each charge case. Typically, the detonating cord terminates proximate to the ends of the perforating gun. In this arrangement, a detonator at one end of the perforating gun can detonate all of the perforating charges in the gun and continue a ballistic transfer to the opposite end of the gun. In this fashion, numerous perforating guns can be connected end to end with a single detonator detonating all of them.
The detonating cord is typically detonated by a detonator triggered by a firing head. The firing head can be actuated in many ways, including but not limited to electronically, hydraulically, and mechanically.
Expendable hollow carrier perforating guns are typically manufactured from standard sizes of steel pipe with a box end having internal/female threads at each end. Pin ended adapters, or subs, having male/external threads are threaded one or both ends of the gun. These subs can connect perforating guns together, connect perforating guns to other tools such as setting tools and collar locators, and connect firing heads to perforating guns. Subs often house electronic, mechanical, or ballistic components used to activate or otherwise control perforating guns and other components.
Perforating guns typically have a cylindrical gun body and a charge tube, or loading tube that holds the perforating charges. The gun body typically is composed of metal and is cylindrical in shape. Within a typical gun tube is a charge holder designed to hold the shaped charges. Charge holders can be formed as tubes, strips, or chains. The charge holder will contain cutouts called charge holes to house the shaped charges.
It is generally preferable to reduce the total length of any tools to be introduced into a wellbore. Among other potential benefits, reduced tool length reduces the length of the lubricator necessary to introduce the tools into a wellbore under pressure. Additionally, reduced tool length is also desirable to accommodate turns in a highly deviated or horizontal well. It is also generally preferable to reduce the tool assembly that must be performed at the well site because the well site is often a harsh environment with numerous distractions and demands on the workers on site.
Currently, perforating guns are often assembled and loaded at a service company shop, transported to the well site, and then armed before they are deployed into a well. Sometimes perforating guns are assembled and armed at the well site. Because the service company shop often employs a single gun loader, maintaining close control on the gun assembly/loading procedures can become difficult. Accordingly, quality control on the assembled/loaded guns may be improved by reducing the amount of assembly necessary at the service company shop.
Many perforating guns are electrically activated. This requires electrical wiring to at least the firing head for the perforating gun. In many cases, perforating guns are run into the well in strings where guns are activated either singly or in groups, often separate from the activation of other tools in the string, such as setting tools. In these cases, electrical communication must be able to pass through one perforating gun to other tools in the string. Typically, this involves threading at least one wire through the interior of the perforating gun and using the gun body as a ground wire.
When typical a perforating gun is assembled/loaded either at the well site or at a service company shop, there is risk of incorrect assembly or damage to electrical wiring or other components that may cause the perforating gun or other tools to fail to fire or fail to function appropriately. For example, the threading of a pass-through wire through the gun body or charge holder presents numerous opportunities for the insulation of the wire to be stripped on sharp metal edges resulting in shorts in the communications circuit. Accordingly, there is a need for a system that eliminates the need to run a wire through a perforating gun body.
Typically, perforating guns and other tools are connected to each other electrically at the well site. This requires that a worker bring the guns or tools close together and then manually make a connection with one or more wires. This requires time and manpower at the well site and introduces the possibility of injury or assembly error. Accordingly, there is a need for a system that eliminates the requirement for workers to make wire connections between perforating guns or tools at the well site.
As discussed above, perforating guns and other tools are often connected with subs that also house related electronic and/or ballistic components. In order to eliminate these subs, a system is needed to house these electrical and ballistic components inside of perforating guns or other tools in an interchangeable and modular way. Additionally, current perforating guns typically have the same diameter and female threads on both ends. In order to eliminate the subs, a perforating gun system that provides male threads on one end of the gun and female threads on the other is needed.